Experimental study on local damage to reinforced concrete panels subjected to oblique impact by projectiles

Okuda, Yukihiko; Nishida, Akemi; Kang, Z.; Tsubota, Haruji; Li, Y.

Journal of Nuclear Engineering and Radiation Science, 9(2), p.021801_1 - 021801_12, 2023/04

https://doi.org/10.1115/1.4054040

Most empirical formulas were proposed to evaluate the local damage to reinforced concrete (RC) structures based on impact tests conducted with a rigid projectile at an impact angle normal to the target structure. Only a few impact tests were performed involving a soft projectile. Therefore, in this study, we conducted a series of impact tests to evaluate the local damage to RC panels subjected to normal and oblique impacts by rigid and soft projectiles. This paper presents the test conditions, test equipment, test results, and obtained knowledge on local damage to RC panels subjected to normal and oblique impacts.

User's manual and analysis methodology of probabilistic fracture mechanics analysis code PASCAL Ver.5 for reactor pressure vessels

Takamizawa, Hisashi; Lu, K.; Katsuyama, Jinya; Masaki, Koichi*; Miyamoto, Yuhei*; Li, Y.

JAEA-Data/Code 2022-006, 221 Pages, 2023/02

JAEA-Data-Code-2022-006.pdf:4.79MB

As a part of the structural integrity assessment research for aging light water reactor (LWR) components, a probabilistic fracture mechanics (PFM) analysis code PASCAL (PFM Analysis of Structural Components in Aging LWR) has been developed in Japan Atomic Energy Agency. The PASCAL code can evaluate failure probabilities and failure frequencies of core region in reactor pressure vessel (RPV) under transients by considering the uncertainties of influential parameters. The continuous development of the code aims to improve the reliability by introducing the analysis methodologies and functions base on the state-of-the-art knowledge in fracture mechanics and domestic data. In the first version of PASCAL, which was released in FY2000, the basic framework was developed for analyzing failure probabilities considering pressurized thermal shock events for RPVs in pressurized water reactors (PWRs). In PASCAL Ver. 2 released in FY 2006, analysis functions including the evaluation methods for embedded cracks and crack detection probability models for inspection were introduced. In PASCAL Ver. 3 released in FY 2010, functions considering weld-overlay cladding on the inner surface of RPV were introduced. In PASCAL Ver. 4 released in FY 2017, we improved several functions such as the stress intensity factor solutions, probabilistic fracture toughness evaluation models, and confidence level evaluation function by considering epistemic and aleatory uncertainties related to influential parameters. In addition, the probabilistic calculation method was also improved to speed up the failure probability calculations. To strengthen the practical applications of PFM methodology in Japan, PASCAL code has been improved since FY 2018 to enable PFM analyses of RPVs subjected to a broad range of transients corresponding to both PWRs and boiling water reactors, including pressurized thermal shock, low-temperature over pressure, and normal operational transients. In particular, the stress intensi

Uncertainty quantification of seismic response of nuclear reactor building using a three-dimensional finite element model

Choi, B.; Nishida, Akemi; Li, Y.; Takada, Tsuyoshi

Earthquake Engineering and Resilience (Internet), 1(4), p.427 - 439, 2022/12

https://doi.org/10.1002/eer2.35

no abstracts in English

Stability of allowable flaw angles for high toughness ductile pipes subjected to bending stress in the ASME Code Section XI

Hasegawa, Kunio; Strnadel, B.*; Li, Y.; Lacroix, V.*

Journal of Pressure Vessel Technology, 144(6), p.061202_1 - 061202_6, 2022/12

https://doi.org/10.1115/1.4054620

When pipe walls are thin, part-through flaws are easily develop into through-wall flaws, and the likelihood of coolant leakage is high. The ASEM Code Section XI provides final allowable flaw angles of through-wall flaw for thin-wall pipes. The final allowable angles are applied to pipes in order to maintain structural integrity if the part-through flaws become through-wall flaws. To ensure that this stability is compromised, plastic collapse stresses for through-wall flaws are combined with allowable stresses. However, the final allowable angles of through-wall flaws are not identified for thin-walled pipes. This paper compares plastic collapse stresses of through-wall flaws and allowable stresses of part-through flaws for pipes. The comparison of these stresses is used to derive the final allowable angles of through-wall flaws. The angles can be expressed either in the form of exact solutions or as conventional options that are appropriate for various service level conditions.

"Southwestern" boundary of the island of inversion; First study of low-lying bound excited states in V and V

Elekes, Z.*; Juhsz, M. M.*; Sohler, D.*; Sieja, K.*; Yoshida, Kazuki; Ogata, Kazuyuki*; Doornenbal, P.*; Obertelli, A.*; Achouri, N. L.*; Baba, Hidetada*; et al.

Physical Review C, 106(6), p.064321_1 - 064321_10, 2022/12

https://doi.org/10.1103/PhysRevC.106.064321

The low-lying level structure of V and V was investigated for the first time. The neutron knockout reaction and inelastic proton scattering were applied for V while the neutron knock-out reaction provided the data for V. Four and five new transitions were determined for V and V, respectively. Based on the comparison to our shell-model calculations using the Lenzi-Nowacki-Poves-Sieja (LNPS) interaction, three of the observed rays for each isotope could be placed in the level scheme and assigned to the decay of the first 11/2 and 9/2 levels. The (,) excitation cross sections for V were analyzed by the coupled-channels formalism assuming quadrupole plus hexadecapole deformations. Due to the role of the hexadecapole deformation, V could not be unambiguously placed on the island of inversion.

Improvement of the return mapping algorithm based on the implicit function theorem with application to ductile fracture analysis using the GTN model

Mano, Akihiro; Imai, Ryuta*; Miyamoto, Yuhei*; Lu, K.; Katsuyama, Jinya; Li, Y.

International Journal of Pressure Vessels and Piping, 199, p.104700_1 - 104700_13, 2022/10

https://doi.org/10.1016/j.ijpvp.2022.104700

Elastic-plastic analyses based on finite element methods are widely applied to simulate the nonlinear behaviors of materials. When the analysis is conducted by an implicit method, the stress values are generally updated with a time increment by using the so-called return mapping algorithm. This algorithm requires solving simultaneous nonlinear equations related to a constitutive model. In the present paper, we proposed a general method to reduce the number of equations in the return mapping algorithm based on the implicit function theorem. In addition, the proposed method was applied to the Gurson-Tvergaard-Needleman (GTN) model that considers the influence of damage due to nucleation and growth of microscopic void in materials in the simulation of the nonlinear behaviors. By using the GTN model with the proposed method, an elastic-plastic analysis was performed by the implicit method for a 4-point bending test of pipe with a through-wall crack. The numerical solution of the variation of the load-load line displacement from the analysis agreed with experimental result. Thus, we concluded that the proposed method is useful for simulating nonlinear behaviors, including void nucleation and growth in materials.

Allowable cracks related to penetration for part-through cracks in pipes subjected to bending stresses

Hasegawa, Kunio; Li, Y.; Strnadel, B.*; Udyawar, A.*

Journal of Pressure Vessel Technology, 144(5), p.051305_1 - 051305_6, 2022/10

https://doi.org/10.1115/1.4053482

Fully plastic collapse stresses for circumferentially part-through cracked pipes subjected to bending stresses are estimated by Limit Load Criteria provided by the ASME Code Section XI. Allowable crack depths were determined by using the Limit Load Criteria and that are tabulated in the ASME Code Section XI for different plant service level conditions. On the other hand, crack penetration bending stresses for part-through cracked pipes were estimated by using the Local Approach of Limit Load Criteria. By using these Criteria, the study presented in this paper obtained allowable crack depths at penetration for circumferentially part-through cracked pipes. Comparing the allowable crack depths obtained by both methods for each service level, it is evident that the allowable crack depths at penetration calculated by the Local Approach of Limit Load Criteria are almost always smaller than those at fully plastic collapse stresses calculated by the Limit Load Criteria. It was found that the allowable crack depths provided by the ASME Code Section XI are less conservative for crack penetrations.

Analytical study for low ground contact ratio of buildings due to the basemat uplift using a three-dimensional finite element model

Choi, B.; Nishida, Akemi; Shiomi, Tadahiko; Kawata, Manabu; Li, Y.

Proceedings of 29th International Conference on Nuclear Engineering (ICONE 29) (Internet), 6 Pages, 2022/08

In the seismic evaluation of nuclear facility buildings, basemat uplift-the phenomenon during which the bottom of the basemat of a building partially rises from the ground owing to overturning moments during earthquakes-is a very important aspect because it affects not only structural strength and integrity, but also the response of equipment installed in the building. However, there are not enough analytical studies on the behavior of buildings with a low ground contact ratio due to basemat uplift during earthquakes. In this study, we conducted a simulation using a three-dimensional finite element model from past experiments on basemat uplift; further, we confirmed the validity of this approach. In order to confirm the difference in the analytical results depending on the analysis code, the simulation was performed under the same analytical conditions using the three analysis codes, which are E-FrontISTR, FINAS/STAR and TDAPIII, and the obtained analysis results were compared. Accordingly, we investigated the influence of the difference in adhesion on the structural response at low ground contact ratio. In addition, we confirmed the effects of significant analysis parameters on the structural response via sensitivity analysis. In this paper, we report the analytical results and insights obtained from these investigations.

Failure bending stresses for small diameter thick-wall pipes

Yamaguchi, Yoshihito; Hasegawa, Kunio; Li, Y.; Lacroix, V.*

Proceedings of ASME 2022 Pressure Vessels and Piping Conference (PVP 2022) (Internet), 4 Pages, 2022/07

Failure estimation methods for steam generator tubes with wall-thinning or crack

Yamaguchi, Yoshihito; Mano, Akihiro; Li, Y.

Proceedings of ASME 2022 Pressure Vessels and Piping Conference (PVP 2022) (Internet), 10 Pages, 2022/07

The steam generator (SG) tube is one of the important components in pressurized water reactors. Flaws such as wall-thinning or stress corrosion cracking have been reported in SG tubes. The burst pressure where both the internal and external pressures from the primary and secondary coolant systems are considered must be predicted to assess the structural integrity of SG tubes. Burst tests were performed by various organizations. On the basis of the test results, failure estimation methods were proposed. In this study, previous burst test data and existing failure estimation methods for SG tubes with wall-thinning or crack were investigated. As a result, the coefficient of the existing estimation method for SG tube with uniform wall-thinning was updated. In addition, failure estimation methods that are suitable for SG tubes with crack or local wall-thinning were proposed by considering the effects of the flaw shape and size on the burst pressure. The applicability of the failure estimation methods was confirmed by comparing the predicted results with the burst test data in actual SG tubes.